Trends change in teen pregnancy among adolescent women in Ethiopia based on Ethiopian demographic and health surveys: Multivariate decomposition analysis

Background Teenage pregnancy may adversely affect their health, economic, and social life. Evidence shows that no studies in Ethiopia used decomposition analysis to identify factors for the trend change in teen pregnancy. Therefore, this study aimed to examine the trends and identify contributing factors to teen pregnancy in Ethiopia using multivariate decomposition analysis. Method We obtained the data on adolescent women from three Ethiopian Demographic and Health Surveys. A weighted sample of 3266 in 2005, 4009 in 2011, and 3381 teenagers in 2016 were involved in this study. Statistical analysis was performed using STATA 14. Multivariate decomposition analysis was used to identify contributing factors to the change in teen pregnancy. The coefficient value with a 95% confidence interval was used to identify significant factors associated with teen pregnancy. Results The prevalence of teen pregnancy in Ethiopia decreased significantly from 15.9% [95% CI: 14.3, 17.7] in 2005 to 12.5% [95% CI: 10.8, 14.3] in 2016. Multivariate decomposition analysis showed that approximately 83% of the overall change in teen pregnancy over time was due to differences in women’s composition. Age, marital status, education status, working status, contraceptive use, and sexual status before age 18 were statistically significant contributing factors to the decline in teen pregnancy over time. Conclusion The prevalence of teen pregnancy in Ethiopia decreased significantly over time. The overall decline in teenage pregnancy is due to differences in population composition. Public health interventions should focus on changing cultural norms or attitudes regarding early marriage and pregnancy within religious leaders and uneducated communities.

Study variables Dependent variable. The outcome variable was teenage pregnancy, which consists of currently pregnant at data collection time, having a child, and terminated pregnancy included in this study. It is referring the percentage of teenagers who are mothers, pregnant with their first child, and have begun childbearing. The response variable is a binary outcome variable present by a random variable Y i for the ith teenager, which has two possible values coded as "1" if the teenager experienced the pregnancy before age 20 and "0" if not experienced the pregnancy before 20 years. Independent variables. The independent variables included in this study were age, place of residence, marital status, educational status, respondents' working status, sex of the household head, age of the household head, early sexual intercourse, mass media exposure, wealth index, and contraceptive use. Relevant independent variables were obtained from the EDHS datasets.
Data management and analysis. Data cleaning, coding, and analysis were performed using Stata 14 software. Sampling probability is vital to handle sampling bias and restore the representative sample. We carried out cross-tabulation and summary statistics to describe the study population. Multicollinearity between two variables can be checked using the variance inflation factor (VIF). If the VIF value is usually less than 10%, there is no multicollinearity assumption between independent variables. Data on adolescent women for this study were obtained from the Women's Recode (IR file) datasets, with a weighted sample size of 3266, 4009, and 3881 teenagers from 2005, 2011, and 2016 EDHS included in it. We appended datasets together to perform trend and decomposition analysis after extracting relevant variables from EDHS 2005, 2011, and 2016. The coefficient value with a 95% confidence interval was used to identify significant independent variables associated with teenage pregnancy.
Multivariate decomposition analysis of the change in teen pregnancy was used to identify the major contributing factors to the change in the percentage of teen pregnancy over the study period. The decomposition analysis targeted how the change in teen pregnancy responds to the differences in respondent or women's characteristics and how these variables shape the changes across the survey conducted at different times. It is a regression analysis of the differences in the percentage of teen pregnancy between EDHS 2005 and EDHS 2016. The purpose of using the multivariate decomposition analysis is to identify the potential source of the differences in the percentage of teen pregnancy in the last decades of ten years. The multivariate decomposition analysis for the non-linear response model uses the output of logistic regression analysis because it is a binary outcome to divide the observed difference in the percentage of teen pregnancy between the surveys into the components. The differences in the composition of the population (Endowment) and the difference in the effect of the characteristics (Coefficient) are essential to identify the factors contributing to the change in teen pregnancy prevalence over time. The change in teen pregnancy prevalence is additively decomposed into women's composition change between the surveys (Endowment) and the difference in the effect of selected independent variables (Coefficient).
The recent EDHS 2016 and baseline EDHS 2005 surveys were denoted by A and B, respectively.
For logistic regression, the log-odds or logit of teen pregnancy can be decomposed as: |ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl {zffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl } |ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl {zffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl ffl } C Where: E represents endowments explained by characteristics, and C represents coefficients not explained.
We can rewrite the above equation as follow: Currently developed multivariate logistic decomposition analysis for the non-linear response model used for the decomposition analysis of teen pregnancy using mvdcmp STATA package [36].

Ethical consideration
An authorization letter was obtained from the online publicly available DHS measure program to access and download the datasets by describing the purpose of the study and used only for this study. This study used the secondary data of publicly available survey data from the Measure DHS program since we did not need ethical approval. We downloaded the datasets for this current study from the website http://www.dhsprogram.com. Datasets obtained from the Measure DHS program are kept confidential.

Background characteristics of the study population
A total of 32666, 4009, and 3881 adolescent women were included in the study. More than a fifth-sixth (84.1%) of the teenagers have not experienced pregnancy, and 12.9% in 2016 were pregnant. Based on the age of teenagers, more than sixty percent (60%) of all study participants were in the age group 15 to 17 years (Table 1). According to the sex of the household head, more than three-quarters (75%) of the households were led by males. Rural and unmarried teenagers comprised more than 73% in all three consecutive surveys.
Regarding maternal educational level, the proportion of teenagers with no formal education revealed a high decline from 40% in 2005 to 13.9% in 2016. However, the proportion of adolescent women with primary education increased from 43.6% in 2005 to 63.5% in 2016. Based on the place of residence, more than 74% of the teenagers were rural residents. The proportion of Orthodox Christians decreased from 52.2% in 2005 to 42.2% in 2016. But Protestants and Muslims increased from 18.5% and 26.3% to 25% and 31.5%, respectively.
Across the three surveys, the proportion of women who experienced early sexual intercourse (before 18 years old) decreased from 24.6% in 2005 to 21.9% in 2016. In the three consecutive surveys, 92% of teenagers did not use contraception. Approximately thirty-one (31%) of adolescent women from all surveys were poor ( Table 1).

Prevalence of teenage pregnancy in Ethiopia
The prevalence of pregnancy among teenagers in Ethiopia decreased from 15

Trends in the prevalence of teen pregnancy by selected characteristics
Trends of pregnancy among teenagers revealed the variation based on different characteristics. The percentage point change in teen pregnancy decreased in many categories of the variables in each phase ( Table 2).
According to educational status, there was an increase in the percentage of pregnancy among teenagers with primary and secondary or above education in the last phase (2005-2016) by 1.9% and 1.4%, respectively. Teenagers who were married/or living together with their partners and Orthodox religious followers revealed a decrement in the prevalence of teen pregnancy with 5.7% and 7.2% point change, respectively. Additionally, women who had used contraceptive methods showed a decrement in teen pregnancy prevalence with a 13.8% point change ( Table 2).

Decomposition analysis of teen pregnancy in Ethiopia, 2005-2016
A general trend decomposition analysis showed a significant decrease in the prevalence of teen pregnancy in Ethiopia. The decomposition results revealed that the decline in teen pregnancy

PLOS ONE
Trends of teen pregnancy among adolescent women in Ethiopia prevalence over the study periods was explained only by the difference in the selected women's characteristics between the two survey points. However, the decline in teen pregnancy prevalence due to the differences in the effect of the selected independent variables was not statistically significant (Table 3).

Differences due to characteristics (Endowment)
Multivariate decomposition analysis results revealed that the overall decline in teen pregnancy was due to the difference in characteristics (the differences in the composition of women's selected variables) between the two survey points (Table 3). Age, marital status, employment status, education level, contraceptive use, and having sex before 18 years of age contributed to the change in the prevalence of teen pregnancy (Table 4).
Multivariate decomposition analysis showed that the age, marital status, respondents' working status, educational status, contraceptive use, and early sexual intercourse were statistically significant variables for the change in teen pregnancy prevalence. The decrement in the proportion of women aged between 18 and 19 in the sampled population revealed a significant positive 1.21% contribution to the decline in the prevalence of teen pregnancy. A decrease in the composition of women who were married/or living together with partners in the sampled population showed a significant inverse effect on the prevalence change in teen pregnancy by 19.88%. The decline in widowed/divorced/separated population composition contributed a positive 0.83% to the decline in teen pregnancy prevalence (Table 4). An increase in the proportion of teenagers with primary education had a statistically significant effect on the change in teenage pregnancy. The compositional changes of women with primary education over the study periods (from 2005 to 2016) showed a significant 23.1% negative contribution to the change in teen pregnancy. A decrease in the proportion of respondents who had no job or

PLOS ONE
Trends of teen pregnancy among adolescent women in Ethiopia were not working over the study periods (from 2005 to 2016) showed a significant 13.3% positive contribution to the decline in teen pregnancy ( Table 4). The decrease in the proportion of women who did not use contraceptive methods contributed to a significant decline in the prevalence of teenage pregnancy, contributing to a 10.25% point change. Moreover, teenagers who had not experienced early sexual intercourse before age 18 in the sample showed a significant positive 10.49% contribution to the decrease in the prevalence of teen pregnancy ( Table 4).
Notice that the negative signs on the percentage changes in teen pregnancy show that compositional changes in characteristics have a negative or reversal effect on teen pregnancy.

Discussion
Teenage pregnancy is a predominant public health challenge in the well-being of one's health and childbirth outcomes. This study assessed the trends and the contributing factors for the change in teen pregnancy in Ethiopia using the EDHS 2005-2016. The trend changes in teen pregnancy prevalence declined significantly from 15.9% in 2000 to 12.5% in 2016. This finding is consistent with studies conducted in sub-Saharan Africa and Ethiopia, which have shown a declining trend in teenage pregnancy [37,38]. The possible reason could be the government and non-government organizations have taken various measures or interventions to create a favorable environment for teenagers to access reproductive health care services and to change cultural attitudes within the communities towards early marriage. Healthcare providers offer health education in the communities to change their perception of early marriage and pregnancy practices.
In the decomposition analysis, the prevalence of teen pregnancy declined significantly over the study periods. Therefore, understanding the potential sources of variation in teenage pregnancy has public health implications for identifying factors to change in teen pregnancy prevalence and evaluating and designing strategies for reproductive health care services. Approximately 83% of the overall decline in teen pregnancy over the last ten years was due to the differences in women's composition over the study periods; the difference due to the differences in the effect of explanatory variables (behavioral changes) was not significant.
A decrement in the proportion of adolescent women aged between 18 and 19 from 20005 to 2016 showed a significant 1.2% negative effect on the decline in teen pregnancy. Besides, as the age of women has increased, there is an increased likelihood of experiencing pregnancy before age 18. This finding is compatible with the studies conducted in Ethiopia and Nigeria [19,20,22]. The reason could be their reproductive life increases with age since they are more exposed to biological and social factors, specifically marriage [19]. The possible explanation might be most teens mothers were more active in sexual intercourse and marriage due to their family's history. It implies they are tending a greater risk of pregnancy and childbirth-related complications.
A decrement in the composition of women who were not working jobs revealed a significant positive effect on the change in the prevalence of teen pregnancy, contributing to 13.3% of the changes. This finding is consistent with a previous study in Ethiopia, Nigeria, and East Africa, in which women who had no job were more likely to experience teen pregnancy [21, 24,37]. The possible reason might be women who had no work or were unemployed in work activities are to be economically dependent, at high risk of school dropout rate, and are prone to harmful practices in early marriage and pregnancy. This result reinforces the contribution of working jobs to achieve positive health outcomes. A decrement in the proportion of women who did not use contraceptive methods showed a significant 10.25 positive contribution to the decline in the prevalence of teen pregnancy. This finding is consistent with prior studies conducted in Ethiopia and Baltimore [22,39]. The reason might be Teenagers may be unable to argue the use of condoms or partners' fidelity, leaving them at higher risk of STDs and unintended pregnancy [40,41]. They are embarrassed to find information about where to find contraceptive methods and how to use these methods during sexual intercourse since they lack access to basic health care and reproductive health care services [40]. Teenagers who become pregnant before reaching 18 years have a higher risk of mother and infant mortality due to pregnancy-related complications. Additionally, unprotected sex increases the distribution of sexually transmitted infectious diseases like HIV and other health-related problems.
The composition changes of teenagers who had experienced early sexual intercourse before age 18 showed positive contributions to the decline in teen pregnancy prevalence. A decrement in the composition of women who experienced early sexual intercourse revealed a significant 10.49% positive contribution to a decrease in teen pregnancy prevalence. This finding is consistent with prior studies in Ethiopia, Baltimore, and Johannesburg [38,39], in which early sexual initiation is more associated with early pregnancy due to a lack of adequate information about reproductive health care services and unmet need for contraception [42]. Besides, forced sexual intercourse is another challenge that predisposes teenagers to premarital sex harassment causing early pregnancy [30]. This result indicated that experiencing early sexual intercourse is a major leading cause of early pregnancy, fistula, unsafe abortion, and death.
An increment in the proportion of women with primary education showed a statistically significant effect on the change in teen pregnancy. This study is compatible with other studies done in Ethiopia [38,43], Nigeria [20], South Asia [44], and Philippes [26], in which girls in school are less likely to engage in sexual activity and become pregnant at an early age. The explanation is that women with formal education may have better knowledge to refuse early marriage and pregnancy at a young age and may understand the lifelong negative consequences on their health and children. In addition, educated women could know the benefit of accessing sexual health care services to delay pregnancy, control unsafe abortion, and avoid unintended pregnancy. Staying longer in school may delay the onset of getting marriage and childbirth.
A decrease in the composition of women who were married/or living together with partners over time showed a significant effect on the change in teen pregnancy. This finding is consistent with other studies conducted in Ethiopia and Japan [21,23]. The reason might be women or teenagers could have low involvement in decision-making to utilize reproductive health care services, particularly any contraceptive method to prevent early pregnancy. The Ethiopian government has formulated rules and regulations to protect against the harmful practice of early marriage and control sexual and reproductive health problems.

Strengths and limitations of the study
The strength of this study was the use of large-scale data sets for obtaining appropriate weighted sample size. We also used decomposition analysis to analyze the contributing factors for the change in teen pregnancy. In addition, consider sampling methods to adjust the nonresponse rate and restore the nationally representative sample.
As a limitation of this study, this secondary data did not measure relevant variables during data collection time; religious beliefs towards marriage, family structure, perception of family planning, decision-making involvement, psychological, social support, and cultural norms. Furthermore, our model is limited to EDHS datasets to explain the difference in the response variable. We recommend future researchers use another alternative method to the decomposition analysis.

Conclusion
Teen pregnancy prevalence decreased significantly in the last decades. However, the pregnancy rate among adolescent women is still high in Ethiopia. Complications during pregnancy and childbirth are leading to the death of mothers and infants. Approximately five-sixth of the overall decline in teen pregnancy prevalence was only due to the difference in the composition of women's characteristics. The significant differences due to the compositional changes in women's selected factors were age, educational level, respondents' working status, contraceptive use, and early sexual intercourse before age 18. It implied that the effectiveness of the health care programs and systems in society suffers from women's characteristics. Furthermore, design planners and decision-makers should scale up health education opportunities in communities to change their attitudes about cultural beliefs and norms of early marriage and pregnancy.